diff --git a/test/functional/forknotify.py b/test/functional/forknotify.py
--- a/test/functional/forknotify.py
+++ b/test/functional/forknotify.py
@@ -6,6 +6,10 @@
 #
 # Test -alertnotify
 #
+"""Test the -alertnotify option."""
+
+import os
+import time
 
 from test_framework.test_framework import BitcoinTestFramework
 from test_framework.util import *
@@ -42,13 +46,19 @@
         self.nodes[1].generate(1)
         self.sync_all()
 
+        # Give bitcoind 10 seconds to write the alert notification
+        timeout = 10.0
+        while timeout > 0:
+            if os.path.exists(self.alert_filename) and os.path.getsize(self.alert_filename):
+                break
+            time.sleep(0.1)
+            timeout -= 0.1
+        else:
+            assert False, "-alertnotify did not warn of up-version blocks"
+
         with open(self.alert_filename, 'r', encoding='utf8') as f:
             alert_text = f.read()
 
-        if len(alert_text) == 0:
-            raise AssertionError(
-                "-alertnotify did not warn of up-version blocks")
-
         # Mine more up-version blocks, should not get more alerts:
         self.nodes[1].generate(1)
         self.sync_all()